Conventionally, each 3-D image display unit, which uses a CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), or the like to display 3-D images, has shifted two images in the eye-width direction to obtain a parallax between those images, then display those shifted images on the screen so as to be recognized by the right and left eyes of the user separately. The user thus comes to recognize a 3-D image configured by those two images.
The patent document 1 (official gazette of Unexamined Published Japanese Patent Application No. 16351/1995) discloses a 3-D display game machine that changes over 3-D images to ordinary 2-D images forcibly in the case where a preset 3-D view allowable play time is reached. The patent document 2 (official gazette of Unexamined Published Japanese Patent Application No. 333479/1994) discloses an image display unit that has an internal timer used to turn off the unit power forcibly in the case where the first predetermined time is reached after the unit is powered. After that, the unit is not powered until the second predetermined time is reached. This is to prevent the unit from a long continuous time use.